Troubleshooting Tip: BGP router-id not updating

The FortiGate updates the BGP router-id if the router-id has been updated manually using the command:

config router bgp

    set router-id x.x.x.x

end

However, if the router-id has been applied automatically, and if that IP is not available now on the FortiGate, the router-id is updated by the BGP process only when the following steps have been done.

1. The device is rebooted.
2. The process <bgp> has been manually restarted. The process can be restarted with the following command:

 FGT# fnsysctl killall bgpd

Example: 

If the router-id has been selected automatically, which has been explained in this article: Technical Tip: BGP router-id selection criteria on FortiGate, and any one of the loopback interfaces IP has been selected for the router-id, and now that interface has been deleted, and the router-id is not updating, in that case, rebooting the device or the process is required.

Note:

Router-ID uses dotted decimal representation like an IPv4 IP, but it is not an IP; it is not a requirement to use an IP configured on the device. 

Related article:
Technical Tip: How to check the BGP router-id using the CLI